1. Field of the Invention
The present invention relates to a reel shaft sensor device of a barcode printer, and in particular to a reel shaft sensor device applicable to a label printer and comprised of magnetic elements and a magnetic sensor for detecting the rotational status of a reel shaft of a barcode printer.
2. The Related Arts
A conventional barcode printer includes reel shafts for continuously supplying a carbon ribbon and a tape of labels. The conventional barcode printer does not include functions to monitor the rotation of the reel shafts thereof, and it often employs open-loop control to determine the rotational speed and status of the reel shafts. However, such a control arrangement may be affected by the inertia and mechanical frictions of the reel shaft itself to thereby induce error. For barcode printers that require precision of control and quality of the rotation of the reel shaft, such positional or angular error often leads to adverse influence for the industry.
If known photoelectric sensors are employed to detect the rotation status of a reel shaft, then it will encounter a problem of complication of installation. In addition, the photoelectric sensor element surfer light pollution problems. For example, when the photoelectric sensor element is arranged outside of the reel shaft, the results of detection might be influenced by natural lights. In addition, the size of the known photoelectric sensor makes it difficult to be installed inside the reel shaft. Installing the known photoelectric sensor inside the reel shaft may also affect the precision and quality of detection by the reel sensor for barcode printers.